Continued advances in proton exchange membrane fuel cells offer a promising solution to current energy needs. Current research is focused on fabrication techniques that improve performance and reduce overall cost. Catalyst deposition on membrane electrode（MEA） assemblies has been used by a number of techniques over the last few decades, divided into two main categories： chemical and physical methods. Of these, physical methods are widely used due to the simplicity of the preparation process and the uniformity of the deposition distribution. The aim of this paper is to review many of the main techniques that have been published in order to demonstrate the wide variety of physical methods of catalyst preparation.

During the operation of a vertical axis wind turbine, the interaction between the upper and lower surface boundary layer and the shear layer causes the formation of periodic vortex structure in the downstream wake of the wind turbine, which has an important effect on the aerodynamic characteristics of the wind turbine. Based on this, the CFD method is used to study the wake vortex structure of vertical axis wind turbine under different working conditions. Fast Fourier transform and phase space trajectory are used to analyze the vortex shedding phenomenon and wake vortex structure of wind turbine blade under different tip speed ratios. The fractal dimension is used to study the torque and wake flow velocity variation. The results show that the wake vortex structure of the wind turbine presents different characteristics with the change of the tip speed ratio. When the tip speed ratio is 3.6, the two sides of the wind turbine wake show regular reverse shedding vortex mode. The wake of the vertical axis wind turbine with low tip ratio has obvious chaotic characteristics, and the chaotic characteristics gradually weaken with the increase of the tip ratio. With the increase of the tip speed ratio, the fractal dimension of wind turbine torque and downstream speed decreases continuously, and when the tip speed ratio is 3.6, the fractal dimension of downstream speed of wind turbine is only 1.07.

An in-depth study on the dynamic aerodynamic performance of the pitch oscillating airfoil is carried out in the two-dimensional test section of the NF-3 low-speed wind tunnel of Northwestern Polytechnical University. The test model is a span-wise three-section force measurement model, and the force measurement is only performed in the middle section of the model to reduce the influence of the sidewall interference of the wind tunnel. In the experiment, the transient angle of attack of the model is collected; the inertial force and pitch moment on the middle section of the model are calculated and subtracted from the data collected by the balance to correct the influence of the model's inertia on the results. The results show that the angle of attack exceeding the positive or negative static stall angles of attack is a necessary condition for the lift and pitch moment coefficients to produce a large hysteresis loops. As the oscillation reduced frequency increases, the dynamic stall is delayed, the lift coefficient hysteresis loop increases, the drag coefficient increases, and the pitch moment coefficient near the maximum angle of attack decreases. When the angle of attack is less than the static angle of attack of stall or exceeds a small range, with the increase of the reduced frequency of the airfoil oscillation, the pitch moment coefficient of the airfoil decreases when it goes up and increases when it goes down. With the increase of the oscillation amplitude, the hysteresis loops of both dynamic lift coefficient and pitch moment coefficient of the oscillating airfoil increase. As the average angle of attack increases, the angle of attack of airfoil enters the positive stall zone more, the lift coefficient hysteresis loop increases, and the minimum pitch moment coefficient decreases. The Reynolds number has no obvious effect on the hysteresis loop of lift, drag and pitch moment coefficients; however, in the downward process, as the Reynolds number increases, the lift recovery advances, and the hysteresis loop decreases.

Theoretical calculations of solar radiation and TRANSYS meteorological system are used for the calculation and characterization of radiation resources. Derive the radiation from the radiation of a typical day of the month for the extraterrestrial, horizontal and inclined surfaces, as well as the total monthly and annual radiation of total and direct radiation. And analyze the total, direct radiation under different percentages of insolation. Use TRANSYS to simulate the change of total and direct radiation of the horizontal and inclined surfaces outside the earth. The results of calculation and analysis show that the total annual solar radiation for the area of Ordos Darat Banner is 9916 MJ/m ², and the total annual solar radiation for the inclined plane is 7675 MJ/m ². There is a big difference between the horizontal and inclined plane radiation. The simulation method of this paper is also applicable to the calculation of solar radiation in any area.

In order to improve the prediction accuracy of the wake velocity in the vertical direction, an improved Jensen wake model is proposed in this paper, which is based on the assumption that the wake velocity presents a polynomial distribution in the vertical direction, and considering the influence on the natural wind speed at different heights on the wake velocity. A single wind turbine is taken as the research object, three models （Jensen model, Gaussian model and improved Jensen model） are used to simulate the wake velocity of the wind turbine respectively. On the basis of the improved Jensen model, the influence of atmospheric stability on wake velocity recovery is analyzed. The simulation results show that the accuracy of the improved wake model is better than that of Jensen model and Gaussian model, and the errors of the improved wake model are as low as 7.35%, 2.82% and 3.44% at 2.5 D , 4.0 D and 8.0 D downstream （ D is the diameter of the wind wheel）. The recovery of wake velocity is closely related to atmospheric stability. The more stable the atmospheric turbulence intensity is, the less conducive it is to the recovery of wake velocity.

This paper aims to explore the comprehensive impact of roller shade on daylighting and energy consumption of office buildings in range of hot summer and cold winter, and determine the key parameters affecting the comprehensive performance of roller shade. Firstly, 560 kinds of roller shade are obtained by selecting the combination of 6 parameters affecting the performance of roller shade, and the annual dynamic energy consumption simulation and daylighting simulation are carried out by using EnergyPlus and Radiance; Secondly, through the questionnaire, the shading schedule considering the human behavior of office buildings and the proportion of indoor personnel’s attention to glare, daylighting and energy consumption are obtained; Finally, considering energy consumption, glare and daylighting, an innovative comprehensive performance index （Energy-Daylight, ED） is proposed to comprehensively evaluate the roller shade. Based on this index, the key parameters affecting the performance of roller shade are determined. The results show that in range of hot summer and cold winter, solar transmittance and reflecttance are two main factors affecting the comprehensive performance of roller shade. When the solar transmittance changes in the range of 0.01~0.10, it has a positive impact on the comprehensive performance of roller shade.

In this paper, a typical rural area in northern Shaanxi province was investigated, Monte Carlo simulation was used to generate aggregated shiftable load curves on the basis of family clustering, and a comprehensive evaluation from the perspectives of time, energy, and randomness was given. The results show that the volume of cooking load is large but the time range to be shifted is small, while the volume of laundry load is small but the time range to be shifted was large. Overall, domestic hot water load is more comprehensive in the above three aspects, the heat storage properties of water tank makes the shiftable load potential more significant.

In order to study the coupling between the wind turbine power and each link of the unit and the influence on the output power of the unit, a double-fed wind turbine is used as an example, Firstly, the energy functions of each subsystem are derived taking into account the tower shadow effect, wind shear and wind speed. Then, the energy variation of each subsystem and the oscillation characteristics of the unit output power are analyzed considering the damping of the turbine and wind speed variation. Finally, the power propagation mechanism and power oscillation characteristics of wind turbine are analyzed through energy changes on the PSCAD/EMTDC platform. The simulation results show that the energy of each subsystem increases greatly when the low frequency oscillation power of the turbine passes through the negatively damped DFIG. The output power of the turbine contains low frequency oscillation and sub-synchronous oscillation, and the amplitude and frequency of oscillation vary with wind speed and damping of the turbine. The energy consumed by the DFIG is mainly determined by the wind turbine subsystem when the wind speed changes.